1. Field of the Invention
This invention relates to methods and structures which utilize hydraulic fluids for bearing a supported surface relative to a supporting surface, with a space between such surfaces, and, more particularly, to methods and structures which utilize hydraulic fluids for bearing a supported surface relative to a supporting surface, with a space between such surfaces, without requiring either the recirculation of hydraulic fluid escaping past the periphery of the space between the surfaces, or the contact of the surfaces with seals designed to prevent such escape of the hydraulic fluid.
2. Description of the Prior Art
Hydrostatic bearings for bearing a supported surface relative to a supporting surface, with a space between the two bearing surfaces, are known. Typically, such bearings are of one or the other of two general types. A first of these general types is designed for use in a recirculating fluid system, such as will be further identified hereinafter. The other general type of known hydrostatic bearing employs one or more seals which contact both the supported surface and the supporting surface of the bearing in order to contain the hydraulic fluid.
A typical recirculating fluid system, as associated with a hydrostatic bearing, includes a pump for causing hydraulic fluid to flow through a space between two surfaces, i.e., a supporting surface and a supported surface. The pump provides sufficient pressure to the fluid for flotation of the supported surface relative to the supporting surface, such that neither surface contacts the other. The hydraulic fluid escapes past the periphery of the space between the two, non-contacting surfaces, and is collected and returned to the pump for recirculation. Recirculating fluid systems are generally considered quite adequate for relatively low pressure hydraulic bearing systems, e.g., of the order of 3,000 p.s.i. or less, but are not suitable for operation at very high pressures due to the excessive power requirement which would be involved in simultaneously recirculating a hydraulic fluid and maintaining it at a very high pressure level. Some examples of recirculating fluid systems may be found in U.S. Pat. Nos. 3,322,473 to J. L. Lebach and 3,442,560 to J. G. C. De Gast.
In the case of a hydrostatic bearing which employs one or more seals for contacting both a supported surface and a supporting surface of the bearing, such seals are utilized in order to avoid leakage of the hydraulic fluid past the periphery of the space between the two surfaces, while a pressure is maintained in the fluid by a pump in order that the supported surface may float relative to the supporting surface. A higher pressure capability is generally sought through the use of such an arrangement, the higher pressure capability, of course, permitting the bearing to handle a relatively large load using a relatively small surface area. However, surface-contacting seals are subject to wear where, as is ordinarily the case, relative movement takes place between the supported surface and the supporting surface. Such wear, of course, is greatest under relatively high load and/or relatively high surface speed conditions. An example of a hydrostatic bearing which employs seals is provided by U.S. Pat. 3,841,719 to G. R. Smith.
Efforts have previously been made to reduce leakage of hydraulic fluid past the periphery of the space between the supported and supporting surfaces of a hydrostatic bearing without the use of seals. In U.S. Pat. No. 2,347,663 to O. A. Carnahan, for example, it is indicated that fluid leakage, in hydrostatic bearing structures associated with plungers which constitute components of a fluid pump or motor, may be minimized, but not eliminated, through a judicious choice of bearing dimensions.
A technique for bearing a supported surface relative to a supporting surface without seals, and without loss of a fluid through a gap at the periphery of a space between the two surfaces, is taught in U.S. Pat. No. 3,570,281 to W. C. Albert. Such patent discloses the use of a liquid metal, such as mercury, as the bearing fluid, in supporting the gimbal of a gyroscope. The density of the suggested liquid metal, its inherently high surface tension characteristic, and its non-wettability combine to prevent its escape through the peripheral gap. While the pressures and loads which can be handled by the liquid metal bearing are not specified, it is quite clear from the nature of the liquid metal medium that only relatively small loads, with relatively low fluid pressures, are involved.
In order to handle relatively very large bearing loads, utilizing relatively small surface areas, while avoiding wear problems associated with excessive wear of seals under high load conditions, it would clearly be desirable to provide techniques and structures which afford a hydrostatic bearing the capability of operating at a relatively very high pressure in a non-recirculating hydraulic system, without resort to the use of seals, and with substantially no leakage of hydraulic fluid past the periphery of the space between the supported and supporting surfaces of the bearing.